IGFBP4

IGFBP4 (Insulin-like Growth Factor Binding Protein 4) is a protein that in humans is encoded by the IGFBP4 gene. It is a member of the insulin-like growth factor binding protein (IGFBP) family and encodes a protein with an IGFBP domain and a thyroglobulin type-I domain. The protein binds both insulin-like growth factors (IGFs) I and II and circulates in the plasma. Binding of this protein prolongs the half-life of the IGFs and alters their interaction with cell surface receptors.

Function

IGFBP4 is one of six binding proteins (IGFBP1-6) that have high affinity for IGF-I and IGF-II. IGFBP4 inhibits IGF-mediated growth and developmental rates. IGFBP-4 binds to IGF-I and IGF-II with relatively high affinity, and exhibits a particularly high affinity for IGF-II. This binding protein is located in the cytoplasm and nucleus, and can either inhibit or enhance the biological activities of IGFs, possibly modulating the functions of these growth factors in various tissues.

Clinical Significance

Alterations in the IGFBP4 gene and its protein product have been implicated in a variety of diseases. For example, increased expression of IGFBP4 has been associated with breast cancer, prostate cancer, and colorectal cancer. In contrast, decreased expression of IGFBP4 has been linked to osteoporosis and rheumatoid arthritis.

See Also

• Insulin-like growth factor
• Insulin-like growth factor binding protein
• IGFBP1
• IGFBP2
• IGFBP3
• IGFBP5
• IGFBP6